# Physics

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A uniform plank of lent light 5m and weight 225N Rests horizontally on two supports with 1.1m of the plank hanging over the right support. To what distance,X, can a person weighing 450 walk On the overhanging part of the plank before it just begins to tip?

• Physics -

Sorry for the typos. It should say, "of length"

• Physics -

The sum of torques has to be zero. So, the sum respectively the reference point (the right support) is
225•1.4 = 450•x
x=225•1.4/450 = 0.7 m

• Physics -

Why does it have to be zero?

• Physics -

The two conditions of equilibrium are:
1. Concurrent Equilibrium : the sum of vector forces through a point is zero.
2. Coplanar equilibrium: the sum of forces in a plane is zero and the sum of the torques around the axis of the plane is zero.
Here we've used the 2nd rule

• Physics -

Should the 1.4 that you used be 1.1?

• Physics -

1.4 is the distance between the center of the plank (its center of mass) and right support.
1.4 = (5/2)-1.1

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